From 1136f7eedc47d2dc0b7ed5af7b7d365e1a734a66 Mon Sep 17 00:00:00 2001
From: Alexander Munch-Hansen <alexmunchhansen@gmail.com>
Date: Wed, 18 Sep 2019 17:28:45 +0200
Subject: [PATCH] Now with group stuff. ElGamal works ish

---
 week4.py | 67 +++++++++++++++++++++++++++++++++-----------------------
 1 file changed, 39 insertions(+), 28 deletions(-)

diff --git a/week4.py b/week4.py
index 5d16dd1..3d4693e 100644
--- a/week4.py
+++ b/week4.py
@@ -2,7 +2,9 @@
 # The one represents our bloodtype. Bob will then encrypt 8 values using these PKs, where each value repredents
 # A truth value, thus either true or false, s.t. each cipher is an entry in the bloodtype comptability matrix.
 
-import secrets
+from secrets import SystemRandom
+import time
+from math import pow
 import numpy as np
 from crypto.week1 import BloodType, convert_from_string_to_enum, blood_cell_compatibility_lookup
 
@@ -18,51 +20,47 @@ convert_bloodtype_to_index = {
 }
 
 
-class Group:
-    def __init__(self, q):
-        self.order = q
-
-    def gen_group_stuff(self):
-        my_group = []
-        for i in range(1, self.order):
-            if np.gcd(i, self.order) == 1:
-                my_group.append(i)
-        for group_ele in my_group:
-            if group_ele**self.order == 1 % self.order:
-                gen = group_ele
-        return gen, self.order, my_group
-
 class ElGamal:
-    def __init__(self, G, g, q):
-        self.group = G
+    def __init__(self, g, q):
         self.gen_ = g
         self.order = q
         self.pk = None
         self.sk = None
 
+    def gen_key(self):
+        key = SystemRandom().randint(1, self.order)
+        while np.gcd(q, key) != 1:
+            key = SystemRandom().randint(1, self.order)
+        return key
+
     def gen(self, sk):
-        h = self.gen_**sk
+        h = (self.gen_**sk) % self.order
         self.sk = sk
         self.pk = (self.gen_, h)
         return self.pk
 
     def enc(self, m, pk):
         # sample random r \in Zq
-        r = secrets.SystemRandom().randint(1, self.order-1)
+        r = SystemRandom().randint(1, q)
+
         g, h = pk
-        c = (g ** r, m * h**r)
-        return c
+        s = (h**r) % q
+        p = (g**r) % q
+        c = s * m
+        return c, p
 
     def dec(self, c):
         c1, c2 = c
-        m = c2 * c1**(-self.sk) # % self.order
+        # c, p, key, q
+        h = (c2**self.sk) % q
+        m = c1 / h
         return m
 
     def ogen(self, r):
         # Here, q = 2p+1, thus we actually need to use the p here, instead of
         # self.order, but as we do not know p yet, .e we
         # TODO: Use p instead of self.order, s.t. self.order = 2p+1
-        s = secrets.SystemRandom().randint(1, self.order)
+        s = SystemRandom().randint(1, self.order)
         h = s**2 % self.order
         return self.gen_, h
 
@@ -73,10 +71,10 @@ class Alice:
         self.gen_ = 9
         self.order = 453
         self.b = convert_bloodtype_to_index[convert_from_string_to_enum[bloodtype]]
-        self.sk = secrets.SystemRandom().randint(1, self.order)
+        self.sk = SystemRandom().randint(1, self.order)
 
         self.pk = self.elgamal.gen(self.sk)
-        self.fake_pks = [self.elgamal.ogen(secrets.SystemRandom().randint(0, self.order))
+        self.fake_pks = [self.elgamal.ogen(SystemRandom().randint(0, self.order))
                          for _ in range(7)]
 
     def send_pks(self):
@@ -112,8 +110,21 @@ class Bob:
 
 
 if __name__ == "__main__":
-    group = Group(11)
-    gen, order, my_group = group.gen_group_stuff()
+    p = 199
+    q = 2*p + 1
+    g = SystemRandom().randint(2, q)
+
+    elgamal = ElGamal(g, q)
+    sk = elgamal.gen_key()
+
+    m = 7
+    pk = elgamal.gen(sk)
+    c = elgamal.enc(m, pk)
+    print(c)
+    d_m = elgamal.dec(c)
+    print("decrupted:", d_m)
+
+
+
 
-    print(gen, order, my_group)